Vertical axis gyratory screen



Mam 2L E95@ L. G. sYMONs @9355 VERTICAL AXIS GYRATORY SCREEN Filed June5, 1944 3 Sheets-Sheet l ffg'y/ March Z119 E95@ L. G. SYMONS VERTICALAXIS GYRATORY SCREEN Filed June 5, 1944 3 Sheets-Sheet 2 fz? were 02[07'e27 @ay/Waff@ March 2E, 195@ L.. G. sYMoNs l 295%955 VERTICAL AXISGYRATORY SCREEN Filed June 5, 1944 I s sheetssheet s Patented Mar. 2l,1950 VERTICAL AXIS GYRATORY SCREEN Loren G. Symons, Hollywood, Calif.,assignor to Nordberg Manufacturing Company, Milwaukee, Wis., acorporation of Wisconsin Application `lune 5, 1944, Serial No. 538,788

s claims. l

My invention relates to an improvement in screens and has for onepurpose to provide a screening structure of increased capacity orimproved product or both.

One purpose is to provide a screen of an improved cylindrical type,wherein a thin layer of material is uniformly fed and is subjected toscreening action at all times over the entire area of the screeningmedium.

Another purpose is to provide a screen in which the force of thematerial or the movement of the material against the screening mediumcan be controlled independent of gravity Another purpose is to provide ascreen in which a generally cylindrical element is simultaneouslyrotated and gyrated.

Another purp-ose is to provide a generally cylindrical screen againstthe interior surface of which the material to be screened is normallycentrifugally held, the material being periodically separated from thescreen and re-delivered against the inner surface of the screen, toobtain eicient separation.

Another purpose is to provide a vertically axised screening drum, andmeans for oscillating it.

Another purpose is to provide an improved rotating screen structure.

Another purpose is to provide improved means for increasing thescreening eiiiciency of a rotated vertically axised screening structure.

Gther purposes will appear from time to time in the course of thespecification and claims.

The method which may be carried out with the use of the apparatus hereindescribed and claimed is claimed in my co-pending application Serial No.533,789, filed on June 5, 1944, and now abandoned.

The invention is illustrated more or less diagrammatically in theaccompanying drawings, wherein:

' Figure l is a vertical axial section;

Figure 2 is a top, plan View;

Figure 3 is a section along the line 3 3 of Figure l;

Figure 4 is a diagram.

Figure 5 is a section on an enlarged scale taken along the line 5-5 ofFigure 1.

-Lilre parts are indicated by like characters throughout thespeciiication and drawings.

Referring to the drawings, l indicates any suitable supporting surfaceor member or base upon which is positioned a xed outer housing 2, which.for convenience, is shown as cylindrical. 3 is a fixed hopper having adischarge spout d and an upper ring 5 located within and spaced inwardlyfrom the outer housing 2. 6 is an adjustable bracket or support mountedon the housing 2 and carrying a motor l, with a pulley i3 about whichpass belts 9 which, in turn, pass about the driven pulley Il).

ll generally indicates a rotor structure which is keyed to the pulleyIl). It includes an upper portion i2, to which the pulley is directlysecured, an intermediate portion I3, an upper eccentric portion id, aconnecting portion I5, a lower eccentric portion l5 and a bottom portionil.

i8 is a bottom hub which rotates with the rotor and carries acounterweight I9. 20 is any f suitable bottom nut for tightening andsupporting the entire assembly, and 2l is a top nut. 22 is a sealingmember which rotates with the rotor and holds down the inner member ofthe ball bearing assembly 23.

it is a spacing sleeve which positions the inner member of the ballbearing 25, where it engages with its lower edge, its upper edgeengaging and supporting the inner member of the ball bearing 23. Thesleeve 26 is counterbored to receive the eccentric portion it, and holdsdown and positions the inner member of the ball bearing 2l. The ballbearing assembly is held at its lower side against any suitable shoulderon the rotor portion I5. A roller bearing assembly 28 is indicatedbetween a lower shoulder on the member l5 and the top of the hub I8. 2i]is a plate supported upon a rubber ring 3i) on the supporting member 2dmounted on the outer housing 2. 3l is a bearing sleeve for the ballbearing assemblies 23 and 25. It is drawn upwardly against the plate 29by any suitable bolts 3i. and the clamping ring 33. It will beunderstood that the rotor rotates within and in relation to the sleeve3i. Bil is a sleeve surrounding a lower portion of the rotor andsurrounding the ball bearing assembly 2l and the roller bearing assemblyE8.

3'5 is a sealing ring, integral with 26, interposed between the sleeves3l and 34. The sleeve 3ft also has an interpenetrating sealingconnection with the hub i3, as at 36. The sleeve 31E- is also providedwith a plurality of outwardly eX- tendllg allges 3l, 38. Secured to theupper flange 38 is a top plate or ring 39, which serves as a distributoror feeding plate or ring for the material to be screened, which may bedropped from above through the open top of the housing 2 from anysuitable feeding means not herein shown. Depending from the flange 38are two diametreally opposed radial supports il! which carry verticallyaligned vertically spaced supporting brackets 4i, 42, which extendoutwardly to support any suitable generally cylindrical rotary screenstructure such as the one below described.

Another pair of diametrically opposed supports or ribs 40a are employedwhich extend downwardly from the iiange 38. The members 4B and 40o aresecured at their lower ends to the circumferentially extending ring 46.Any suitable connecting angles m2 may be employed between the members 4Band 40a, and the rings 46, held to the ring for example by bolts m2o.There is a similar securing connection between the below described upperapron 43 and the members 4i) and 49a. 44 is a ring secured to the flange3'? and provided with radially extending arms 45 which are split toreceive the vertical supports 4G and 40a.

43 is an upper generally cylindrical apron which may be unitarily formedwith or permanently secured to the top plate 39 and the ribs or spokes52. The ribs in turn, may be welded or otherwise permanently secured tothe outer top ring d!! with its flanges or ears 5l. For convenience thetop plate 39, the ribs 52, and the outer ring 5i may be formed as asingle welded assembly which may be bolted to the upper iiange of theinner circumferential ring 43. The plate 39 is shown as resting on andsecured to the bottom flange of the outer sleeve 55 which is providedwith an internal friction band 5l adapted to engage the exterior of theXed sleeve 3i.

Referring to the specific means for supporting the screen medium, twoI-beam sections mi diametrically opposed at opposite sides of thedevice, are bolted at their upper ends to the flanges 5| of the top ring4B. At the bottom they are welded to and form part of the outwardlyflanged ring t8 with its outwardly extending flange 50. The supports orangle brackets 4|, 42 and the plate 06 are welded to and unitary withthe members im. Thus the brackets or supports 4i and 42 tie the verticalI-beams securely to the radial ribs or supports 4G. The cylindricalrings 5d are split as at 54a in Figure 5 and pass through notches in thevertical I-beams lill and are bolted to the supports 4I and 42 and tothe intermediate supporting plate 108, for example the countersunk boltsas shown in Figure 5. This assembly makes a cylindrical skeleton aboutwhich the wire cloth or screening medium may be fastened. The rings 54can be renewed individuallf,7 without disturbing the assembly. The wirecloth 53, which I may describe as a screening drum or a screening mesh,may be put on in two halves and held to the screen frame by thehalf-clamp rings H33, and by the clamp bolts fc5 which pass through themembers m4 at the ends of the rings and through the webs of the I-beamslill. To remove the cloth or mesh for replacement, it is necessarymerely to remove the bolts m5, remove the clamp rings m3 and thus freethe cloth. The clamp rings E03 which are T-shaped in cross section aresufficiently rigid to maintain the cylindrical shape of the cloth whensupported only at their ends. It will be noted that the two ribs 49awhich are ninety degrees out of alignment with the ribs 40 are bolted tothe ring 45 only and not to the screen frame proper. If it were not forthese two ribs and the ring 4.6, the component of motion would not bermly transmitted to the screen cloth, as the ribs 4t would be weak inthat direction. The ribs 40 and 40a may be identical in length.

It will be observed that the screen structure as a whole is flexiblysupported and its weight is taken by the yielding exible distortablemember 3g which in turn is supported by the transversely extendingsupport 3i. The entire structure, including the feeding plate 39, isrotated by the friction of the band 5'1 against the sleeve 3| inresponse to rotation of the rotor i5. It will be understood that theband 5l is bolted or otherwise held against movement in relation to thesurrounding sleeve 55. It will be understood that the rate of rotationmay be widely varied, for example, by employing a variable speed motor,although any other suitable means for varying the speed of rotation ofthe pulley I0 may be employed.

The rotation of the rotor is effective to obtain the desired rate ofrotation of the screen cylinder. The eccentricity of the rotor imparts awobble, or gyraticn, to the screen cylinder. I fin-:l that a ratio ofgyrations to revolutions of l5 to 1 is eiective, but it will beunderstood that the gyration rate and the rate of rotation may both bevaried through fairly wide limitation.

It will be realized that whereas I have shown a practical and operativedevice, nevertheless many changes may be made in the size, shape, numberand disposition of parts without departing materially from the spirit ofmy invention. I therefore wish the drawings to be taken as in a broadsense as illustrative or diagrammatic rather than as limiting me to myprecise showing.

For example, in the structure as herein shown in Figure l, the screenstructure is positively rotated by the friction of the band 5l againstthe sleeve 3i in response to rotation of the rotor I 5. The rate ofrotation is governed by the relative diameter of the members El and Si.It will be understood, however, that any other suitable means ofrotating the screening structure such as a chain of gears or V-beltdrives might be employed.

For example whereas I have illustrated a generally cylindrical screeningmedium, it will be understood that in practice, I may departsubstantially from a cylindrical shape. For example, when, in theclaims, I call for a generally cylindrical screening mesh, it will beunderstood that by the term generally cylindrical I wish to includescreening mesh which is not strictly cylindrical, and which may, forexample, depart from the arcuate in transverse cross-section. Also it iswithin the scope of my invention to obtain a combined rotary andgyratory movement of a circumferentially extending screening medium by awide variety of mechanical means.

The use operation of the invention are as follows:

In the structure herein shown, I employ as the separating medium, agenerally cylindrical vertically axised screen element. This screenelement is rotated at a fairly high speed about its `rertical axis. Imay instance a speed of 35 to 4G R. P. M., but the speed may be widelyvaried, depending upon the material treated and the results desired.This speed of rotation determines the force of the impact or thrust ofthe particles against the cloth. The particles are fed to the interiorof the cylinder of mesh and frictionally take a speed approximating thespeed of rotation of the mesh. Thus, they are centrifugally urged ormoved outwardly against the inner face of the mesh. Hence, the speed ofrotation determines the thrust of the particles against the cloth, andalso determines the force of the impact which takes place when the clothis removed from the particles and again receives them. v

I obtain this separation by gyrating the cloth, or the screening unit,at a rate which may run in the order of to 1, in relation to the rate ofrotation. As shown in the diagram, Figure 4, this gyration of the clothcreates an alternate separation of the particles from the cloth,followed by an ensuing contact or impact of the particles against thecloth.

Referring to the diagram, X represents a true circle. Y represents thepath of a given point on the screen cloth. Z represents the approximatepath the material takes when the cloth is outwardly withdrawn in thecourse of its gyration. When the outward withdrawal of the cloth freesthe particles, they move generally tangentially until they are againcontacted by the cloth as the cloth moves inwardly in the course of itsgyratory movement.

In use, I employ changes in the rate of rotation to control thecentrifugal force with which the material is urged outwardly against themedium. Incidentally since the rate of gyration varies with the rate ofrotation, the degree of acceleration of the particles under gravity,between contacts with the screen, also varies with changes in the rateof rotation. However, it is particularly important that, in the use ofmy screen, I can control the force of the material against the medium,which would be the equivalent of controlling the weight of the materialon a at screen. The particles are not urged against the medium bygravity but by centrifugal force. This force is directed radiallyoutwardly, as the particles and the screen are traveling at virtuallythe same rate when the particles again contact the screen after theyhave been released from the screen by the gyratory movement of themedium.

I employ the terms screen, mesh, cloth and separating mediuminterchangeably, but it will be understood that a relatively ne screencloth may advantageously be employed for ne screening in accordance withmy invention. However, a variety of screening mesh or separating mediamay be employed.

In the actual use of the invention herein described, the medium may beconsidered as rotating or moving at a relatively rapid rate about a Zoneof treatment dened by and surrounded by the medium. The medium ispreferably generally vertical, so that the gravital thrust on theparticles is in general parallelism with the inner face of the medium.This is not strictly necessary, but is convenient. Under somecircumstances a more or less conic medium may be employed.

The material is initially outwardly fed against the upper part of theinner face of the medium. I may employ the centrifugal feeding plate 39,but other means may be employed. This top plate 39 is rotated at thesame speed as the medium or screen 53 itself. The particles arecentrifugally accelerated and pass across the relatively narrow gapbetween the outer edge of the plate 39 and the screen cloth 53, or theupper ring 49, which may initially receive the particles.

The space circumferentially dened by and adjacent the inner face of themedium may be thought of asconstituting a zone of treatment. Theparticles pass circumferentially around this may be widely varied inorder to suit the particuzone of treatment. They hug the inner face ofthe medium and are rotarily conveyed by the medium at approximately thespeed of rotation of the medium. Because of the generally circular pathof the medium, the particles adhere to its inner face, except as theymay be temporarily separated from it by the gyratory action. Were it notfor the gyratory action, each individual particle would hug the innerface of the medium and there would be little, if any, gravital conveyingmovement, and a minimum of screening action. However, the rapid sequenceof gyration causes a separation of the particles from the inner surfaceof the medium. In eiect, the

particles are deflected inwardly, and the medium is withdrawn outwardlyimmediately afterward. This description is to be taken as illustrativeand approximate. The particles as shown in Figure 4, when released,follow a substantially rectilinear path until they reengage the innerface of the medium.

Thus, the particles are subjected to three main forces. They arecentrifugally held on, and move with the medium rapidly about the zoneof treatment defined by the medium and by the path of movement of themedium. But as they pass around this path, they are freed from themedium at frequent intervals and are recontacted after each interval offreedom. During the short period of freedom, the particles are subjectedto gravital force and move slightly downwardly across the face of themedium. Thus, a typical, individual particle will reengage the medium alittle nearer to its lower edge. As will be seen from the diagram ofFigure 4, each particle may be free from the medium and subjected to theforce of gravity lfor about seventy-ve percent of the time taken by itspassage across the medium from top to bottom. However, considered inseconds, or fractions of seconds, the elapsed time of any single periodof freedom is so slight that the acceleration under gravity is limited.Thus, even though the particles may be theoretically free of the mediumfor seventy-live percent of the time, nevertheless, they travelrelatively slowly downwardly across the medium, and are subjected to alarge number of screening contacts during this travel.

As, by varying the rate of rotation of the medium, I can vary theeffective weight of material on the screen cloth, I may apply myinvention to a wide variety of screening problems. In eiect, I increasethe weight or thrust of the material against the screen by increasingthe rate of rotation. For example in screening or bolting flour I maysubstantially increase the rate of rotation and gyration, thus causingthe flour to push very heavily on the screen cloth. The weight ofmaterial screened per hour may be reduced. In bolting fiour as high asninety-eight percent of the volume of material treated may go throughthe medium to obtain a thorough separation. It is therefore desirable torotate the medium at a relatively high speed. But where the mixture ofparticles to be screened has a relatively small volume of nes and mostof the mixture passes over instead of through the medium, it ispractical to reduce the rate of rotation to a substantial degree. Thisreduces the thrust of the material against the medium and increases thetonnage per hour and incidentally the speed of movement of theindividual particles downwardly across the medium. It will be understoodthat the speed of rotation of the medium accuses lar screening `problemto 'he solved, and in order to control or vary the 4thrust of thematerial against the medium.

In considering the details oi the efect on the particles, it will lheunderstood that the medium and the particles move around the zone oftreatment in the same direction and at substantially the same speed.When a particle approaches the medium and is aligned with an aperture inthe medium, its path of movement toward the medium is generally radialVand it therefore passes through any available aperture in the medium.There is no glancing action or slanting angular approach. Thisrelationship of the rate of movement 'of thc medium vand the materialalso results in Iapplying the strongest possible force to releasingover-sized particles. Also, a general result of the avoidance of shearbetween the particles and the medium is a great reduction in the rate ofwear of the medium. This is highly important, for example in connectionwith a medium formed of very ne `cloth of metal, silk or the like.

It will therefore be Seen that my invention permits of great flexibilityin solving a wide variety of screening problems. It may be applied tothe screening of materials that vary greatly in weight, from lightground grains for example, to heavy metallic ores, and to the greatintermediate range of materials.

The result of changes in the rate of rotation can be understood inconnection with the diagram of Figure e. This diagram illustrates thepath of the material and the path of the point on the screen cloth. Atrue circle is indicated at .X. The path of a given point on the screenis indicated by Y :and the path of the material is indicated by 2. Therelation of the speed and amplitude of gyration to the rotation of thescreening medium determines the wave form made by the path of point onthe screen cloth. This wave form determines the height a the materialwill be tossed from the cloth. The amplitude in can be varied bychanging the eccentricity, and the distance between the crests of thewaves can he changed by increasing or decreasing the ratio of gyrationto rotation. can for example create a very small amplitude of vibrationwith a short length of `wave, which might be suitable for screening veryune material, or for screening larger material I may increase theamplitude b and inarease the length of the wave. This can all bedolindependent of gravity, as it affects only the actual screeningimpact and not the gravital control.

It should be kept in mind that I provide a light layer of material feduniformly over all the screen cloth, with all oi the screen cloth ormedium in action all of the time. This involves a maximum capacity, Inthe second place, I provide a mechanism which permits controlling theforce of the material against the screen cloth and thus to control thescreening action independent of gravity. This effects an increase inefficiency and in capacity for example, flour can be made to weighx asmuch as heavy rocks by merely increasing the speed of rotation of themedium.

I claim:

i. In a screening structure, .a base, a generally cylindrical generallyupright screen mesh movably supported upon said base, the interioreiiective screening portion of the screen being substantiallyunobstructed, a driving assembly formed and adapted simultaneously togyrate said mesh and to rotate it about a generally upright gyrated axisat a rotative speed effective to urge particles into conveying contactwith the inner surface of the mesh, said driving assembly being adaptedto impart to said mesh an amplitude of gyration, and a frequency ofgyration in relation to the rotation of the mesh which, together, areadapted intermittently to withdraw the mesh outwardly from the particlesand to return the mesh thereafter into conveying contact with theparticles, and a feeding assembly formed and adapted to deliverparticles against the inner surface of the rotated mesh.

2. The structure of claim 1 characterized by and including ya screenmesh and a driving assembly therefor suspended from the base,

`3. The structure of claim 1 characterized by and including a screenmesh and a driving assembly therefor flexibly suspended -from the base.

4. The structure oi claim 1 characterized by and including a feed platemounted for rotation in unison with and at the same rate of rotation asthe screen mesh, said plate having a discharge edge spaced inwardly fromthe circumference of the mesh.

5. |The structure o claim l characterized by and including a generallyupright drive shaft and a driving connection therefor, said drive shaftbeing supported upon said base, said drive shaft including a lowereccentric portion, said screen mesh being mounted upon said lowereccentric portion, and a driving connection for said screen mesh adaptedto rotate it in response to the gyration imparted to it by the rotationoi the driving shaft, with a fixed and predetermined relationshiphetween the rate of rotation and the rate of gyration.

6. A screening method which includes continuously feeding material ofmixed sizes to the inner surface of a vertical rotating cylinder ofscreening medium under conditions causing the material to attain therotating speed of the cylinder, employing centrifugal force to hold thema erial against the inner surface of the medium, and intermittently`preairing the centrifugal connection between the material and medium byintermittently gyrating the cylinder at rates and amplitudes effectiveto cause continuously changing portions of the material to travelinwardly along the paths approximating chords of circles of thecylinder, while allowing the material to fall freely by gravity aftereach inward impulse until it again contacts the cylinder, andcontrolling the timing of the combined movement of rotation and gyrationof the cylinder to cause the ensuing meeting of the material with thecylinder to take place prior to the maximum inward acceleration of thatportion of the cylinder on the next succeeding gyration, therebyrepeatedly throwing the oversize material inwardly along approximatelychordal paths, while causing the undersize material to continue alongsuch paths through the screening medium.

"1. A screening method which includes rotating a generally uprightcylindrical mesh about a gyrated center at a rotative speed eective tourge particles into conveying contact with the inner surface of themesh, and gyrating said mesh through an amplitude and at a frequency ofgyration in relation to the rate of rotation of the mesh eifective towithdraw any given part of the mesh intermittently outwardly from thecorresponding particles and returning the mesh into contact with saidparticles and thereby moving the particles generally circumferentiallywithin the mesh in a sequence of conveyed excursions in contact with themesh followed by free ights of the particles within but out of contactwith the mesh, each free flight terminating in an ensuing conveyingcontact with the mesh or in an escape through the mesh.

8. The method of screening particles of mixed size which consists indelivering them against the inner face of a generally upright generallycylindrical screening medium and rotating said medium at speedseffective to hold the particles so fed against the inner surface of saidmedium and thereby positively causing and controlling a generally radialthrust of the particles against the inner surface of the medium, whilecausing undersized particles to move through the screening medium, andsimultaneously gyrating the screening medium and using such gyrationintermittently to separate the particles retained within the screeningmedium from contact with the screening medium, and to reengage theparticles with the screening medium, in a succession of conveyedmovements in contact with the screening medium and free ghts within andout of contact with the screening medium.

LOREN G. SYMONS.

10 y l I REFERENCES CITED The following references are of record in thele o-f this patent:

UNTTED STATES PATENTS Number Name Date 521,209 Donovan June 12, 1874292,259 Schutz Jan. 22, 1884 400,620 Winkler Apr, 2, 1889 440,634 HoltNov. 18, 1890 549,365 Jones et al. Nov. 5, 1895 901,519 Burke Oct. 20,1909 1,138,741 Fowler May 11, 1915 1,222,903 Symons Apr. 17, 19171,455,907 Damon May 22, 1923 2,204,835 Traylor June 18, 1940 2,416,499Saxe Feb. 25, 1947 FOREIGN PATENTS Number Country Date 437,751 GreatBritain Nov. 5, 1935 6,581 France Oct. 27, 1906 563,239 France Sept. 21,1923

